Control valve for cooling circuit

ABSTRACT

A control valve that forms part of a cooling circuit comprising a first branch which contains a radiator and a second branch that constitutes a bypass of a radiator, and its method of use, are described. 
     When used in a motor vehicle combustion engine cooling circuit, the control valve has a third branch and has at least one unit heater for heating the vehicle cabin.

FIELD OF THE INVENTION

The invention pertains to a control valve for a motor vehicle combustionengine cooling circuit, as well as to the circuit thus obtained.

It relates more particularly to a control valve suitable for formingpart of a cooling circuit traversed by a cooling fluid and comprising afirst branch which contains the radiator for cooling the engine, asecond branch which constitutes a bypass of the engine cooling radiator,and one or more third branches which each contain at least one unitheater for heating the cabin.

Conventionally, the cooling fluid is water plus an antifreeze, whichcirculates in a closed circuit under the action of a circulation pump.

Such a cooling circuit uses, in a conventional manner, a thermostaticvalve which comprises a fluid inlet connected to the outlet of theengine and two fluid outlets which correspond, respectively, to thebranch containing the cooling radiator and to the branch forming abypass.

During cold starting of the engine, and as long as the temperature ofthe cooling fluid has not reached a certain threshold, the valvecirculates the cooling fluid around the bypass branch, short-circuitingthe cooling radiator. As soon as the temperature of the cooling fluidreaches and exceeds the aforesaid threshold, the cooling fluid passesthrough the cooling radiator and detours around the bypass branch.

Generally, the cooling fluid circulates continuously around the branchthat contains the unit heater, the heating of the cabin then beingobtained by mixing of a cold air stream and of a hot air stream that hasswept this unit heater. It is also known to provide a separate valve onthe unit heater for adjusting the flow rate of cooling fluid that passesthrough it.

Thus, the known cooling devices require complex means for effecting thedistribution of the cooling fluid between the three aforesaid branches,as a function of the engine operating conditions and of the comfortconditions desired by the occupant or occupants of the vehicle.

One of the aims of the invention is to provide a valve allowingindependent management of the flow rates of the cooling fluid in thevarious branches of the engine cooling circuit.

The invention is also aimed at producing such a valve that makes itpossible to optimize and to improve the various functions, in particularwhile the temperature of the combustion engine is rising and when cabinheating is desired, and also in the event of overheating of the engine.

The invention is also aimed at providing such a valve that possesses amotorized manner of operation and that possesses a more dependablemanner of operation than conventional thermostatic valves.

To this end, the invention proposes a control valve of the type definedin the introduction, which comprises a body having a fluid inlet, afirst outlet connected to the first branch of the circuit, a secondoutlet connected to the second branch of the circuit and at least onethird outlet connected to the third branch or branches, as well as anadjustment member mounted rotatably in the valve body so as toselectively control the outlets, this adjustment member being suitablefor taking in succession at least the following positions when it isrotated in a given direction;

-   -   a “bypass” position, at which the first outlet is open;    -   a “radiator+bypass” position, at which the first outlet and the        second outlet are open;    -   a “radiator” position, at which the second outlet is open;    -   a “radiator+unit heater” position, at which the second outlet        and the third outlet are open;    -   a “radiator+bypass+unit heater” position, at which the first        outlet, the second outlet and the third outlet are open;    -   a “unit heater+bypass” position, at which the first outlet and        the third outlet are open;    -   a “unit heater” position, at which the third outlet is open;    -   a “zero flow rate” position, at which no outlet is open.

The positions indicated above correspond to those occurring in sequence,when the adjustment member is rotated in the valve body, in a givendirection.

However, it should be understood that the adjustment member may bebrought directly into one of the above positions as a function of aparticular desired mode.

Advantageously, the adjustment member is suitable for furthermore takinga “safety” position which corresponds either to the “radiator” position,at which the second outlet is open, or to the “radiator+unit heater”position, at which the second outlet and the third outlet are open.

These safety positions favor the cooling of the engine while allowingthe heat of the engine to be dissipated, either across the radiatoralone, or across the radiator and the unit heater.

According to another characteristic of the invention, the control valvecomprises control means suitable for bringing the adjustment member

either into one of the positions: “bypass”, “radiator+bypass”,“radiator”, when a no-heating mode is desired,

or into one of the positions: “radiator+unit heater”,“radiator+bypass+unit heater”, “unit heater+bypass”, “unit heater”, whena with-heating mode is desired.

According to yet another characteristic of the invention, the fluidoutlets run into the body through openings of chosen shapes anddimensions, made at chosen locations of said body.

Preferably, the openings of the fluid outlets are of circular generalshape and have different diameters.

In a preferred embodiment of the invention, the body comprises acylindrical lateral wall into which the fluid outlets run at axialheights and at angular positions that are chosen with respect to theaxis of rotation of the adjustment member, while the fluid inlet runsaxially into the body.

It is however possible to envisage an embodiment where the inlets andthe outlets are reversed on the body; for example, the body may comprisethree fluid inlets and one outlet.

In a preferred embodiment of the invention, the adjustment member isembodied in the form of a hollow cylinder comprising through-openingssuitable for controlling the fluid outlets as a function of the angularposition of the adjustment member with respect to the body.

It is however possible to envisage other types of adjustment members,and in particular a member of the disk type.

According to yet another characteristic of the invention, the controlvalve comprises motorization means suitable for driving the adjustmentmember so as to bring it into chosen angular positions with respect tothe valve body. These motorization means may comprise, for example, amotor of the stepper or DC type.

Under another aspect, the invention relates to a cooling circuit for amotor vehicle combustion engine, which is traversed by a cooling fluidunder the action of a circulation pump, which circuit comprises acontrol valve as defined previously, whose fluid inlet is connected toan intake for cooling fluid coming from the engine and whose first fluidoutlet, second fluid outlet and third fluid outlet or outlets areconnected, respectively, to a first branch which contains the coolingradiator for the engine, a second branch which constitutes the bypass ofthe cooling radiator, and one or more third branches which each containat least one unit heater for heating the cabin.

In one preferred embodiment of the invention, this circuit comprises amechanical circulation pump driven by the engine and/or an electriccirculation pump able to be actuated by control means.

Preferably, the electric circulation pump is inserted into the thirdbranch which contains the unit heater, and the control means aresuitable for actuating the electric circulation pump in one of thefollowing positions: “unit heater” position, “radiator+unit heater”position and “radiator+bypass+unit heater” position.

According to one embodiment the circuit in accordance with the inventionmay comprise two or three third branches each containing at least oneunit heater.

Such an embodiment will find its applications particularly in vehiclesin which one wishes to modulate the distribution of heat inside thecabin of the vehicle. It is then advantageous to be able to adjust theheat given off by each of the unit heaters. To do this, hitherto, thequantity of fluid passing through the unit heaters was regulated withthe aid of separate actuators arranged on each of said third branches,the actuators generally being situated at the level of an airconditioning box into which the unit heaters are integrated.

In such a circuit, according to an advantageous embodiment of the valvein accordance with the invention, the heat given off by each unit heatermay be adjusted without resorting to said actuators.

To do this, said valve is furnished for each third branch with acorresponding third outlet communicating with said third branch and theadjustment member is suitable for taking additional positions at whichsaid third outlets are open or otherwise, selectively. It will thus bepossible, as a function of the angular position of said member, to feedjust one, several or all said third branches.

In the description which follows, given merely by way of example,reference is made to the appended drawings, in which:

FIG. 1 is an exploded perspective view of a control valve according tothe invention;

FIG. 2 is a diagram of a cooling circuit of a motor vehicle combustionengine, equipped with a control valve according to the invention;

FIG. 3 diagrammatically illustrates the openings through which the threeoutlets of the valve run into the valve body;

FIG. 4 is a diagram showing a sequence of positions of the valve in afirst embodiment of the invention;

FIG. 5 is a similar diagram in a variant embodiment;

FIG. 6 is a similar diagram in another variant embodiment;

FIG. 7 is a reference curve showing the progressiveness of the openingof the valve outlet which corresponds to the radiator;

FIG. 8 is a similar diagram to that of FIG. 4 in another embodiment ofthe invention; and

FIG. 9 is a flow chart illustrating the manner of operation of the valveof the invention.

The control valve 10 represented in FIG. 1 comprises a body 12 ofcylindrical general shape, delimited by a back wall 14 and a cylindricalwall 16 of axis XX. Into the cylindrical lateral wall 16 run threeoutlet nozzles 18, 20 and 22 at axial heights and at angular positionsthat are chosen with respect to the axis XX. In the example, the nozzles18, 20 and 22 run radially into the wall 16 and they have differentdiameters, as may also be seen in FIG. 3.

In FIG. 3, which is a schematic representation, the openingscorresponding to the nozzles, 18, 20 and 22 are aligned whereas, inreality, they are offset angularly as shown in FIG. 1.

The valve body 12 comprises a circular open face 24 intended to beclosed by a cover 26 which is furnished with a fluid inlet nozzle 28,directed in the direction of the axis XX. The lateral wall 16 of thebody 12 exhibits an inner cylindrical surface 30 delimiting a housing 32for an adjustment member 34. The latter defines an interior cavity 36able to be fed with fluid through the inlet nozzle 28 of the valve.

The adjustment member 34 is embodied in the form of a hollow cylinderable to rotate about the axis of rotation XX. It exhibits anintermediate cylindrical surface 38 furnished with two through-openings40 and surrounded by two other cylindrical surfaces 42 and 44 situatedat the end thereof. The cylindrical surface 42 is furnished with twothrough-openings 46, while the cylindrical surface 44 is furnished withone through-opening 48. The adjustment member is able to take variousangular positions under the action of control means MC (representeddiagrammatically) which comprise a motorization, for example a stepperor DC motor MPP. Thus, the adjustment member 34 can be brought into veryprecise angular positions, thereby making it possible to control thedistribution of the fluid through the outlets 18, 20 and 22.

The seal between the adjustment member 34 and the interior surface 30 ofthe lateral wall 16 is provided by a leaktight seal 50 having the formof a cylindrical cage.

The cover 26 is furnished with three radial lugs 52 through which areintended to pass screws (not represented) cooperating with correspondingbosses 54 exhibited by the valve body.

A leaktight seal 56 of annular shape is arranged between the open face24 of the body 12 and the cover 26. Moreover, the adjustment member 34terminates in a tip 58 surrounded by a leaktight seal 60 and able topass through an opening (not visible in FIG. 1) in the back 14 of thebody 12. In this way, the adjustment member 34 can be rotated by thestepper motor MPP already cited.

Reference is now made to FIG. 2 which shows a circuit 60 for cooling amotor vehicle combustion engine 62. The circuit 60 is traversed by acooling fluid, typically water plus an antifreeze, which circulatesunder the action of a mechanical pump 64 driven by the engine 62,possibly with the aid of an electric pump 66. The fluid heated by theengine, leaves the latter through an outlet 68 which is connected to theinlet nozzle 28 of a control valve 10 of the type described above.

This control valve comprises three outlet nozzles 18, 20 and 22 whichare connected respectively to three branches of the circuit. The lattercomprises a first branch 70 which contains a radiator 72 for cooling theengine 62 and an expansion tank 74, a second branch 76 which constitutesa bypass of the cooling radiator 72, and a third branch 78 whichcontains a unit heater 80 for heating the cabin of the vehicle. Theelectric pump 66 is inserted into the branch 78 which contains the unitheater 80.

The valve 10 allows independent management of the fluid flow rates inthe branches 70, 76 and 78, so as to optimize the temperature of thecombustion engine and the heating of the cabin, under maximum conditionsof safety.

The outlets 18, 20 and 22 of the valve 10 are connected respectively tothe branches 76, 70 and 78. The inlet 28 of the valve 10 is, preferably,connected directly and axially to the outlet 68 of the engine 62.

The actuator that operates the adjustment member 34 (in the example, thestepper motor MPP) is, preferably, an electric actuator that possesses avery small response time which in all cases is less than 1 second. It isthen powered by the vehicle's electrical network and is controlled by asingle wire, in analog or in digital. Diagnosis can be on the same wireas on the preset or on an independent wire in analog or digital.

The actuator is furnished with a member, for example a sensor, making itpossible to ascertain its position in real time, so as to detect anydrift or any malfunction.

As may be seen in FIG. 2, the three fluid outlets 18, 20 and 22 areperpendicular to the axis of rotation XX, while the fluid inlet 28 isarranged axially and opposite the engine so as to minimize the headlosses, in the position where the valve is fully open.

In all the embodiments, the cross sections of the nozzles aredimensioned to allow good flow of the fluid, that is to say withconstant section, with no bend and with progressive shapes.

The fluid outlet 20 (bypass) is situated nearest to the fluid inlet 28,so as to be able to integrate the valve 10 with the combustion engine62, thereby also making it possible to do away with the link piecebetween the outlet 68 of the engine 62 and the inlet 28 of the valve 10.

The adjustment member 34, operated by the actuator MPP, orients anddistributes the flow rate of the cooling fluid. The latter enters thecavity 36 of the adjustment member 34 via the inlet nozzle 28 and isdistributed between the three outlets 18, 20 and 22 by the shape of thethrough-openings 40, 46 and 48 of the adjustment member 34. To eachangular position of the adjustment member 34 there corresponds a welldefined distribution.

In the example represented, the shapes of the through openings of theadjustment member 34 are delimited by circular arcs, but they mayadvantageously be modified to obtain a better progressiveness of theflow rates.

The sequence of the pathways or positions will now be described withreference to FIG. 1, in which the sequence of positions is representeddiagrammatically and the through-openings 40, 46 and 48 of theadjustment member 34 are represented by gray hatched zones. The caserepresented shows a sequence where the three pathways or outlets arearranged one above the other, but all the angular arrangements of thethree outlets are possible while keeping the same sequence. Only a resetis necessary.

If the adjustment member 34 is rotated in a given direction with respectto the body 12 of the valve, this member can take in succession at leastthe following positions:

-   -   a “bypass” position P1, at which the first outlet 18 is open;    -   a “radiator+bypass” position P2 or P3, at which the first outlet        18 and the second outlet 20 are open;    -   a “radiator” position P9 or P10′, at which the second outlet 20        is open;    -   a “radiator+unit heater” position P4 or P10, at which the second        outlet 20 and the third outlet 22 are open;    -   a “radiator+bypass+unit heater” position P6 or P7, at which the        first outlet 18, the second outlet 20 and the third outlet 22        are open;    -   a “unit heater+bypass” position P5, at which the first outlet 18        and the third outlet 22 are open;    -   a “unit heater” position P5′ or P8, at which the third outlet 22        is open; and    -   a “zero flow rate” position P0 or P0′, at which no outlet is        open.

The various aforesaid positions are designated by rectangles in FIG. 4.It is noted that the first three aforesaid positions, namely the“bypass”, “radiator+bypass” and “radiator” positions correspond to ano-heating mode, while the other positions “radiator+unit heater”,“radiator+bypass+unit heater”, “unit heater+bypass” and “unit heater”correspond to a with-heating mode.

Also indicated by rectangles, at the top of the figure, are thebeginning of the opening of the radiator and the end of the opening ofthe radiator. Leaktight zones Z1 and Z2 are situated between the openradiator and closed radiator branches. The perimeter of the adjustmentmember is designated diagrammatically by the letters POR.

The sequences of operations are given again in Table 1 below.

TABLE 1 Engine flow Unit heater Radiator Bypass Operating phases EWPrate flow rate flow rate flow rate Remarks 1: Cold starting, no OffReduced: bypa 0 0 Qeng Valve heating disabled 2: First valve opening, noOff Radia + bypa 0 Regulation Regulation heating 3: Regulation (engineT°), Off Radia + bypa 0 Regulation Regulation no heating 4: Vehiclestationary, On Qewp: radia + unit Qewp Qpost 0 Post-cooling engine off,no heating htr cooling assumption 5: Cold starting with Off Unit Qheatmax 0 Qtoo full heating, high engine revs htr + bypa 5′: Cold startingwith On Unit htr Qheat max 0 0 heating, low engine revs 6: First valveopening, On Radia + bypa + unit Qheat max Regulation Regulation withheating htr 7: Regulation (engine T°), On Radia + bypa + unit Qheat maxRegulation Regulation with heating htr 8: Vehicle stationary, On Unithtr Qheat max 0 0 engine off, with heating 9: Engine overheat at highOff Radia 0 Qmax 0 revs 9′: Engine overheat at low Off Radia 0 Qmax 0Risk of revs On Radia + unit Qunit htr Qmax 0 conflict htrEWP/mechanical pump 10: Safety (ditto 4) On Qewp: radia + unit Qewp:safety Qpost- 0 Deicing + demisting htr flow rate cooling and safetyprotection flow rate against engine overheat 10′: Safety (ditto 9) OffRadia 0 Qmax 0 Engine cooling 0: Cold starting with no Off 0 0 0 0Option engine flow rate

In this table, the first column represents the various phases or modesof operation of the system, the second column represents operation (on)or shutdown (off) of the electric water pump EWP, the third columnrepresents the engine flow rate, the fourth the unit heater flow rate,the fifth column the radiator flow rate, the sixth column the bypassflow rate and the seventh column some remarks. It should be noted thatthe adjustment member can take a “safety” position P10 or P10′ whichcorrespond respectively to the “radiator+unit heater” position, at whichthe second outlet 20 and the third outlet 22 are open and to the“radiator” position, at which the second outlet 20 is open.

This mode of operation favors the cooling of the engine by allowing thedissipation of the heat of the engine either across the radiator alone,or across the radiator and the unit heater.

FIG. 5 is a representation similar to FIG. 4. It differs from the latteressentially in the fact that the leaktight zones Z1 and Z2 have beendispensed with. Moreover, the shapes of the openings corresponding tothe bypass have been substantially modified.

FIG. 6 corresponds to a variant of FIG. 4. The leaktight zones Z1 and Z2are retained but the shape of the opening that corresponds to theradiator has been modified to improve the progressiveness.

Reference is now made to FIG. 7 which shows a curve of progressivenessof the opening of the outlet 20 (radiator outlet) of the valve 10 as afunction of a base control signal 100.

This exemplary embodiment corresponds to flow cross sections having thefollowing diameters: 20 mm for the outlet 20 (radiator), 20 mm for theoutlet 18 of the bypass and 28 mm for the fluid inlet 28.

Here progressiveness is established for operation with a pressure of 1bar and with a cooling fluid temperature of 23° C.±2° C. The flow rateof the radiator increases progressively from the beginning of opening ofthe radiator outlet (outlet 18) up to complete opening which correspondsto 100% of the flow cross section. Here the curve is based on straightline segments that link up with one another, but it could also be formedof a single straight line or of a polynomial.

Reference is now made to FIG. 8 which shows another sequence ofsimplified operation, which here begins with a mode with heating andthen terminates in a mode without heating. The various positions aredesignated by the same symbols P1, P2, etc. as in FIGS. 4 to 6.

Here again one encounters the leaktight zones Z1 and Z2 between the openradiator and closed radiator branches. The corresponding manner ofoperation is illustrated by Table 2 below, in which the column headingsare the same as in Table 1 mentioned above. Table 2, corresponding toFIG. 8, shows a sequence which allows gentle switchover from regulationwith demand for heating to regulation with no demand for heating.

TABLE 2 Unit Engine flow heater Radiator Bypass Operating phases EWPrate flow rate flow rate flow rate Remarks 1: Cold starting, no OffReduced: bypa 0 0 Qeng Disabling of heating the valve 2: First valveopening, no Off Radia + bypa 0 Regulation Regulation heating 3:Regulation (engine T°), Off Radia + bypa 0 Regulation Regulation noheating 4: Vehicle stationary, On Qewp: radia + unit Qewp Qpost 0Post-cooling engine off, no heating htr cooling assumption 5: Coldstarting with Off Unit Qheat max 0 Qtoo full heating, high engine revshtr + bypa 5′: Cold starting with On Unit htr Qheat max 0 0 heating, lowengine revs 6: First valve opening, On Radia + bypa + unit Qheat maxRegulation Regulation with heating htr 7: Regulation (engine T°), OnRadia + bypa + unit Qheat max Regulation Regulation with heating htr 8:Vehicle stationary, On Unit htr Qheat max 0 0 engine off, with heating9: Engine overheat at low Off Radia 0 Qmax 0 revs 10: Safety (ditto 9)Off Radia 0 Qmax 0 0: Cold starting with no Off 0 0 0 0 As an optionengine flow rate

The flow cross sections of the valve, when at least two branches arecommunicating, are calculated in such a way as to limit the pressuredifference between the inlet and the outlet of the valve, below 1 bar,so as not to create too much torque, greater than 1 Nm, at the actuatorlevel.

The sequence of operations of Table 2, like that of Table 1, may beeffected either with an adjustment member 34 of the hollow cylinder typeas described above, or else with any other type of adjustment member, inparticular a member of the disk type.

Reference is now made to FIG. 9 which represents a flow chart of theoperation of the control means associated with the valve 10.

The flow chart shows that the valve 10 is initialized in apre-regulation known position. First means of comparison C1 make itpossible to compare the temperature of the cooling fluid T water withrespect to a critical temperature T water critical which corresponds tothe maximum value that the engine can tolerate as a function of theso-called “material” temperature which corresponds to the temperature ofthe engine. In all cases, the critical temperature of the cooling fluidmust remain below its boiling temperature. In the example, the coolingfluid is regarded as being water plus an antifreeze.

These first means of comparison C1 compare T water with T watercritical. If T water is greater than T water critical, the control meansbring the valve automatically to the “safety” position so as to favorthe cooling of the engine and the demisting of the cabin, if necessary.

Otherwise, the second means of comparison C2, which determine theheating requirement, compare the temperature of the cabin T cab with atemperature T cab preset. T cab represents the temperature measured inthe cabin, whereas T cab preset represents a cabin temperature preset.

If T cab is greater than T cab preset, third means of comparison C3determine whether the heating is ineffective, by comparing thetemperature T water with a minimum threshold temperature T min thresholdwhich corresponds to the minimum temperature of the engine coolingfluid, below which no purpose is served by circulating water around theunit heater, the rising of the engine temperature then being encouraged.

If T water is less than T min threshold, then the valve is brought intothe “bypass” position P1 or into a “zero flow rate” position P0 or P04closing the three pathways and completely shutting off the engine flowrate.

Otherwise, fourth means of comparison C4, which determine the limitationof the unit heater flow rate, compare the engine revs RPM engine with athreshold RPM preset.

If RPM engine is greater than the threshold RPM preset, means ofcomparison C5 compare the temperature T water with a preset temperatureT preset, which corresponds to a water temperature preset temperaturecalculated by the engine cooling computer or the engine computer as afunction of diverse parameters that correspond to the engine and to thevehicle. These parameters may comprise in particular the engine load(intake pressure, throttle or pedal position, engine revs, speed of thevehicle, operation of the air conditioning, pressure of the refrigerantfluid, exterior temperature, etc.).

If T water is greater than T preset, the valve is brought to the“radiator+bypass+unit heater” position (position P6).

Otherwise, the valve is brought into a “unit heater+bypass” position.

In the case where RPM engine is below the threshold RPM preset, means ofcomparison C6 compare T water with T preset. If T water greater than Tpreset, the valve is brought to the “unit heater+radiator” position P7.Otherwise, the valve is brought to the “unit heater” position, that isto say P8 or P5′.

In the case where T cab is less than T cab preset, means of comparisonC7 compare T water with T preset. If T water greater than T preset, thevalve is brought into a “radiator+unit heater” position, that is to sayinto a position P3 lying between P1 and P9. Otherwise, the valve isbrought into the “bypass” position which corresponds to the position P1.

Of course, variant embodiments of the invention are possible. Inparticular, the adjustment member is not limited to a hollow cylinder;it may be solid and truncated by a plane.

1. A control valve of a cooling circuit of a motor vehicle combustionengine, the circuit being traversed by a cooling fluid and comprising afirst branch (70) which contains an engine cooling radiator (72) forcooling the engine (62), a second branch (76) which constitutes a bypassof the engine cooling radiator (72), and one or more third branches(78), each of which contains at least one unit heater (80) for heating amotor vehicle cabin, wherein the valve (10) comprises a body having afluid inlet (28), a first outlet (18) connected to the second branch(76), a second outlet (20) connected to the first branch (70) and atleast one third outlet (22) connected to the third branch or branches(78), as well as an adjustment member (34) mounted rotatably in thevalve body so as to selectively control the outlets (18, 20, 22), andwherein the adjustment member (34) takes the following positionsoccurring in a sequence when rotated in a given direction: a “bypass”position (P1), at which the first outlet (18) is open, followed in thesequence by; a “radiator+bypass” position (P2; P3), at which the firstoutlet (18) and the second outlet (20) are open, followed in thesequence by; a “radiator” position (P9; P10′), at which the secondoutlet (20) is open, followed in the sequence by; a “radiator+unitheater” position (P4; P10), at which the second outlet (20) and thethird outlet (22) are open, followed in the sequence by; a“radiator+bypass+unit heater” position (P6; P7), at which the firstoutlet (18), the second outlet (20) and the third outlet (22) are open,followed in the sequence by; a “unit heater+bypass” position (P5), atwhich the first outlet (18) and the third outlet (22) are open, andfollowed in the sequence by; a “unit beater” position (P5′; P8), atwhich the third outlet (22) is open.
 2. The control valve as claimed inclaim 1, wherein the adjustment member takes a “safety” position (P10)which corresponds to the “radiator+unit heater” position, at which thesecond outlet (20) and the third outlet (22) are open.
 3. A controlvalve of a cooling circuit of a motor vehicle combustion engine, thecircuit being traversed by a cooling fluid and comprising a first branch(70) which contains an engine cooling radiator (72) for cooling theengine (62), a second branch (76) which constitutes a bypass of theengine cooling radiator (72), and one or more third branches (78), eachof which contains at least one unit heater (80) for heating a motorvehicle cabin, wherein the valve (10) comprises a body having a fluidinlet (28), a first outlet (18) connected to the second branch (76), asecond outlet (20) connected to the first branch (70) and at least onethird outlet (22) connected to the third branch or branches (78), aswell as an adjustment member (34) mounted rotatably in the valve body soas to selectively control the outlets (18, 20, 22), and wherein theadjustment member (34) takes the following positions occurring in asequence when rotated in a given direction: a “bypass” position (P1), atwhich the first outlet (18) is open, followed in the sequence by; a“radiator+bypass” position (P2; P3), at which the first outlet (18) andthe second outlet (20) are open, followed in the sequence by; a“radiator” position (P9; P10′), at which the second outlet (20)) isopen, followed in the sequence by; a “radiator+unit heater” position(P4; P10), at which the second outlet (20) and the third outlet (22) areopen, followed in the sequence by; a “radiator+bypass+unit heater”position (P6; P7), at which the first outlet (18), the second outlet(20) and the third outlet (22) are open, followed in the sequence by; a“unit heater+bypass” position (P5), at which the first outlet (18) andthe third outlet (22) are open, and followed in the sequence by; a “unitheater” position (P5′; P8), at which the third outlet (22) is open;wherein the adjustment member takes a “safety” position (P10) whichcorresponds to the “radiator+unit heater” position, at which the secondoutlet (20) and the third outlet (22) are open, and, wherein theadjustment member takes a “safety” position (P10′) which corresponds tothe “radiator” position, at which the second outlet (20) is open.
 4. Thecontrol valve as claimed in claim 1, which comprises control meanssuitable for bringing the adjustment member (34): either into one of thepositions; “bypass” (P1), “radiator+bypass”, “radiator” (P9), when ano-heating mode is desired, or into one of the positions: “radiator+unitheater” (P4; P10), “radiator+bypass+unit heater”, “unit heater+bypass”(P5), “unit heater” (P5′; P8), when a with-heating mode is desired. 5.The control valve as claimed in claim 1, wherein the fluid outlets (18,20, 22) run into the body (12) through openings of chosen shapes anddimensions, made at chosen locations of said body (12).
 6. The controlvalve as claimed in claim 5, wherein the openings of the fluid outlets(18, 20, 22) are of circular general shape and have different diameters.7. A control valve of a cooling circuit of a motor vehicle combustionengine, the circuit being traversed by a cooling fluid and comprising afirst branch (70) which contains an engine cooling radiator (72) forcooling the engine (62), a second branch (76) which constitutes a bypassof the engine cooling radiator (72), and one or more third branches(78), each of which contains at least one unit heater (80) for heating amotor vehicle cabin, wherein the valve (10) comprises a body having afluid inlet (28), a first outlet (18) connected to the second branch(76), a second outlet (20) connected to the first branch (70) and atleast one third outlet (22) connected to the third branch or branches(78), as well as an adjustment member (34) mounted rotatably in thevalve body so as to selectively control the outlets (18, 20, 22), andwherein the adjustment member (34) takes the following positionsoccurring in a sequence when rotated in a given direction: a “bypass”position (P1), a which the first outlet (18) is open, followed in thesequence by; a “radiator+bypass” position (P2; P3), at which the firstoutlet (18) and the second outlet (20) are open, followed in thesequence by; a “radiator” position (P9; P10′), at which the secondoutlet (20) is open, followed in the sequence by; a “radiator+unitheater” position (P4; P10), at which the second outlet (20) and thethird outlet (22) are open, followed in the sequence by; a“radiator+bypass+unit heater” position (P6; P7), at which the firstoutlet (18), the second outlet (20) and the third outlet (22) are open,followed in the sequence by; a “unit heater+bypass” position (P5), atwhich the first outlet (18) and the third outlet (22) are open, andfollowed in the sequence by; a “unit heater” position (P5′; P8), atwhich the third outlet (22) is open, which comprises motorization means(MPP) suitable for driving the adjustment member (34) so as to bring itinto chosen angular positions with respect to the valve body (12).
 8. Acontrol valve of a cooling circuit of a motor vehicle combustion engine,the circuit being traversed by a cooling fluid and comprising a firstbranch (70) which contains an engine cooling radiator (72) for coolingthe engine (62), a second branch (76) which constitutes a bypass of theengine cooling radiator (72), and one or more third branches (78), eachof which contains at least one unit heater (80) for heating a motorvehicle cabin, wherein the valve (10) comprises a body having a fluidinlet (28), a first outlet (18) connected to the second branch (76), asecond outlet (20) connected to the first branch (70) and at least onethird outlet (22) connected to the third branch or branches (78), aswell as an adjustment member (34) mounted rotatably in the valve body soas to selectively control the outlets (18, 20, 22), and wherein theadjustment member (34) takes the following positions occuring in asequence when rotated in a given direction: a “bypass” position (P1), atwhich the first outlet (18) is open, followed in the sequence by; a“radiator+bypass” position (P2; P3), at which the first outlet (18) andthe second outlet (20) are open, followed in the sequence by; a“radiator” position (P9; P10′), at which the second outlet (20) is open,followed in the sequence by; a “radiator+unit heater” position (P4;P10), at which the second outlet (20) and the third outlet (22) areopen, followed in the sequence by; a “radiator+bypass+unit heater”position (P6; P7), at which the first outlet (18), the second outlet(20) and the third outlet (22) are open, followed in the sequence by; a“unit heater+bypass” position (P5), at which the first outlet (18) andthe third outlet (22) are open, and followed in the sequence by a “unitheater” position (P5′; P8), at which the third outlet (22) is open,which comprises motorization means (MPP) suitable for driving theadjustment member (34) so as to bring it into chosen angular positionswith respect to the valve body (12), and wherein the fluid outlets (18,20, 22) run into the body (12) through openings of chosen shapes anddimensions, made at chosen locations of said body (12).
 9. A controlvalve of a cooling circuit of a motor vehicle combustion engine, thecircuit being traversed by a cooling fluid and comprising a first branch(70) which contains an engine cooling radiator (72) for cooling theengine (62), a second branch (76) which constitutes a bypass of theengine cooling radiator (72), and one or more third branches (78), eachof which contains at least one unit heater (80) for heating a motorvehicle cabin, wherein the valve (10) comprises a body having a fluidinlet (28), a first outlet (18) connected to the second branch (76), asecond outlet (20) connected to the first branch (70) and at least onethird outlet (22) connected to the third branch or branches (78), aswell as an adjustment member (34) mounted rotatably in the valve body soas to selectively control the outlets (18, 20, 22), and wherein theadjustment member (34) takes the following positions occurring in asequence when rotated in a given direction: a “bypass” position (P1), atwhich the first outlet (18) is open, followed in the sequence by; a“radiator+bypass” position (P2; P3), at which the first outlet (18) andthe second outlet (20) are open, followed in the sequence by; a“radiator” position (P9; P10′), at which the second outlet (20) is open,followed in the sequence by; a “radiator+unit heater” position (P4;P10), at which the second outlet (20) and the third outlet (12) areopen, followed in the sequence by; a “radiator+bypass+unitheater”position (P6; P7) at which the first outlet (18), the secondoutlet (20) and the third outlet (22) are open, followed in the sequenceby; a “unit heater+bypass” position (P5), at which the first outlet (18)and the third outlet (22) are open, and followed in the sequence by; a“unit beater” position (P5′; P8), at which the third outlet (22) isopen, which comprises motorization means (MPP) suitable for driving theadjustment member (34) so as to bring it into chosen angular positionswith respect to the valve body (12), and wherein the fluid outlets (18,20, 22) run into the body (12) through opening of chosen shapes anddimensions, made at chosen locations of said body (12) and wherein theopenings of the fluid outlets (18, 20, 22) are of circular genera1 shapeand have different diameters.
 10. A cooling circuit for a motor vehiclecombustion engine (62), which is traversed by a cooling fluid under theaction of a circulation pump (64; 66), which circuit comprises thecontrol valve (10) as claimed in claim 1, whose fluid inlet (28) isconnected to an intake (68) for cooling fluid coming from the engine(62) and whose first fluid outlet (18), second fluid outlet (20) andthird fluid outlet or outlets (22) are connected respectively to a firstbranch (70) which contains the cooling radiator (72) for the engine(62), a second branch (76) which constitutes a bypass of the enginecooling radiator (72), and one or more third branches (78) which eachcontain at least one unit heater (80) for heating the cabin.
 11. Thecooling circuit as claimed in claim 10, which comprises a mechanicalcirculation pump (64) driven by the engine (62).
 12. A method ofcontrolling fluid flow in a cooling circuit in a motor vehicle whereinthe circuit being traversed by a cooling fluid during the variousoperating phases of engine operation comprises: a first branch (70)which contains the radiator (72) for cooling the engine (62): a secondbranch (76) which constitutes a bypass of the engine cooling radiator(72): and one or more third branches (78) which each contain at leastone unit heater (80) for heating the cabin, and wherein the coolingcircuit has a control valve (10) comprising a body having a fluid inlet(28), a first outlet (18) connected to the second branch (76), a secondoutlet (20) connected to the first branch (70) and at least one thirdoutlet (22) connected to the third branch or branches (78), and anadjustment member (34) mounted rotatably in the valve body so as toselectively control the outlets (18, 20, 22), such that the adjustmentmember (34) takes the following positions occuring in a sequence whenrotated in a given direction: first, opening to a “bypass”position (P1),at which the first outlet (18) is open, followed in the sequence by;second, opening to a “radiator+bypass” position (P2; P3), at which thefirst outlet (18) and the second outlet (20) are open, followed in thesequence by; third, opening to a “radiator” position (P9; P10′), atwhich the second outlet (20) is open, followed in the sequence by;fourth, opening to a “radiator+unit heater” position (P4; P10), at whichthe second outlet (20) and the third outlet (22) are open, followed inthe sequence by; fifth, opening to a “radiator+bypass+unit heater”position (P6; P7), at which the first outlet (18), the second outlet(20) and the third outlet (22) are open, followed in the sequence by;sixth, opening to a “unit heater+bypass” position (P5), at which thefirst outlet (18) and the third outlet (22) are open, and followed inthe sequence by; seventh, opening to a “unit heater” position (P5′; P8),at which the third outlet (22) is open.
 13. A method as claimed in claim12, wherein the adjustment takes a “zero flow rate” position (P10), atwhich no outlet is open.
 14. A method as claimed in claim 12, whereinthe adjustment member takes a “safety” position (P10) which correspondsto the “radiator+unit heater” position, at which the second outlet (20)and the third outlet (22) are open.
 15. A method as claimed in claim 13,wherein the adjustment member of the control valve is suitable fortaking a “safety” position (P10′) which corresponds to the “radiator”position, at which the second outlet (20) is open.
 16. A method asclaimed in claim 12, wherein the adjustment member (34) is brought by acontrol means: either into one of the positions “bypass” (P1),“radiator+bypass”, “radiator” (P9), when a no-heating mode is desired;or into one of the positions “radiator+unit heater” (P4; P10),“radiator+bypass+unit heater”, “unit heater+bypass” (P5), “unit heater”(P5; P8), when a with-heating mode is desired.